Cooktops having flat glass or ceramic cooking surfaces on which pots, pans or other cooking utensils are placed to be heated are well known in the art. A flat glass ceramic surface has many advantages. It provides a unitary surface which is aesthetically pleasing to the eye, greatly enhances the ease with which the cooktop may be cleaned, and does not require precise positioning of the pot or pan to be heated. Ceramic cooktops are described, for example, in U.S. Pat. No. 6,410,892 issued to Peschl et al. on Jun. 25, 2002 entitled “Cooktop having a flat glass ceramic cooking surface” and in U.S. Pat. No. 6,515,263 issued to Mitra et al. on Feb. 4, 2003 entitled “Cooking stove having a smooth-top glass ceramic cooktop, and a smooth-top glass ceramic cooktop with a glass ceramic cooktop cooking surface, method for production of stoves with smooth-top glass ceramic cooktops and smooth-top glass ceramic cooktops,” the disclosures of which are hereby incorporated herein by reference.
Touch controls and electronic displays have been developed for use with appliances such as cooktops. Touch panels provide a smooth control panel surface for good appearance and easy cleaning and eliminating reliability problems caused by mechanically movable switch contacts. Electronic displays used in combination with touch panel controls can provide an immediate indication to the user in an easily understood manner that the desired control function has in fact been selected and allow the user to ascertain at a glance the state of the controls, i.e., the last control operation.
U.S. Pat. No. 5,097,113 issued to Aoyama on Mar. 17, 1992 entitled “Touch switch arrangement for a heating cooking appliance” describes a heating cooking appliance that includes a heater for the cooking, a touch control switch that produces an operation signal when being touched by the user's finger, and a microcomputer for controlling the heater so that energization of the heater is initiated whenever the operation signal generated by the switch is continuously input into the microcomputer for a predetermined period of time.
U.S. Pat. No. 4,121,204 issued to Welch et al. on Oct. 17, 1978 entitled “Bar graph type touch switch and display device” describes a control for use with a cooktop consisting of an array of light transmitting touch sensitive switches that together provide a lighted, segmented bar graph display. A control circuit responsive to the touch sensitive area of each switch is connected for driving the segments of the bar graph such that, when any one of the switches is touched, a corresponding display segment and all display segments to one side of that segment are energized and the remaining display elements are de-energized.
For electrically nonconductive control surfaces that are periodically soiled and must be conveniently and often cleaned, like glass ceramic cooktops, capacitive touch controls possess significant advantages. In conventional arrangements, these touch controls are typically discrete switches. For example, two buttons are commonly associated with each burner to adjust a continuous quantity (e.g., heat) up or down. One must repeatedly hit increment and decrement to obtain the desired parameter value. This is counter to the way one interacts in the natural, continuous world, where one normally sets a continuous, analog value. Even in the world of cooktops, the knobs that still are ubiquitous on a standard range are continuously rotated to set the desired heat level.